This invention relates to monitoring systems for capacitor batteries, and more particularly, to a system for monitoring a capacitor battery in an AC voltage network, the capacitor battery consisting of a number of parallel legs, each with a number of series-connected sectional capacitors with fuses, adjacent ones of the sectional capacitors being connected to one another.
Capacitor batteries are used, for example, in wattless power compensation in AC or rotary voltage networks. In general, such capacitor batteries consist of a number of parallel legs, each of which contains a number of sectional capacitors, each sectional capacitor being connected in series with a fuse. Adjacent sectional capacitors are coupled to one another through continuous cross lines. A multiplicity of sectional capacitors may be contained in one capacitor battery. When a sectional capacitor short circuits, the adjacent, interconnected sectional capacitors discharge via the cross lines and through the fuse which is in series with the shorted sectional capacitor. Such a defect causes the fuse to open-circuit.
When a sectional capacitor in a capacitor battery fails, such as by short circuiting, the fundamental frequency component of the capacitor current changes only slightly, thereby rendering detection of a shorted sectional capacitor difficult to achieve with known current monitoring or current measuring systems. This problem is compounded by the fact that, in large capacitor batteries having many sectional capacitors, variations in capacitor current as a result of temperture changes may be greater than current changes caused by failure of one or more sectional capacitors.
It is, therefore, an object of this invention to provide a monitoring system for a capacitor battery in an AC voltage network which reliably detects the failure of one or more sectional capacitors using measurement techniques.